Question: Vanessa did 18 fewer sit-ups than Tiffany in the morning. Vanessa did 2 sit-ups. How many sit-ups did Tiffany do?
Answer: Vanessa did 2 sit-ups, and Tiffany did 18 more than that, so find the sum. The sum is $2 + 18$ sit-ups. She did $2 + 18 = 20$ sit-ups.